// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_CHILD_CHILD_PROCESS_H_
#define CONTENT_CHILD_CHILD_PROCESS_H_

#include <memory>

#include "base/macros.h"
#include "base/synchronization/waitable_event.h"
#include "base/threading/thread.h"
#include "content/common/content_export.h"

namespace content {
class ChildThreadImpl;

// Base class for child processes of the browser process (i.e. renderer and
// plugin host). This is a singleton object for each child process.
//
// During process shutdown the following sequence of actions happens in
// order.
//
// 1. ChildProcess::~ChildProcess() is called.
//   2. Shutdown event is fired. Background threads should stop.
//   3. ChildThreadImpl::Shutdown() is called. ChildThread is also deleted.
//   4. IO thread is stopped.
// 5. Main message loop exits.
// 6. Child process is now fully stopped.
//
// Note: IO thread outlives the ChildThreadImpl object.
class CONTENT_EXPORT ChildProcess {
public:
    // Child processes should have an object that derives from this class.
    // Normally you would immediately call set_main_thread after construction.
    ChildProcess();
    explicit ChildProcess(base::ThreadPriority io_thread_priority);
    virtual ~ChildProcess();

    // May be NULL if the main thread hasn't been set explicitly.
    ChildThreadImpl* main_thread();

    // Sets the object associated with the main thread of this process.
    // Takes ownership of the pointer.
    void set_main_thread(ChildThreadImpl* thread);

    base::MessageLoop* io_message_loop() { return io_thread_.message_loop(); }
    base::SingleThreadTaskRunner* io_task_runner()
    {
        return io_thread_.task_runner().get();
    }

    // A global event object that is signalled when the main thread's message
    // loop exits.  This gives background threads a way to observe the main
    // thread shutting down.  This can be useful when a background thread is
    // waiting for some information from the browser process.  If the browser
    // process goes away prematurely, the background thread can at least notice
    // the child processes's main thread exiting to determine that it should give
    // up waiting.
    // For example, see the renderer code used to implement GetCookies().
    base::WaitableEvent* GetShutDownEvent();

    // These are used for ref-counting the child process.  The process shuts
    // itself down when the ref count reaches 0.
    // For example, in the renderer process, generally each tab managed by this
    // process will hold a reference to the process, and release when closed.
    // However for renderer processes specifically, there is also fast shutdown
    // code path initiated by the browser process. The process refcount does
    // not influence fast shutdown. See blink::Platform::suddenTerminationChanged.
    void AddRefProcess();
    void ReleaseProcess();

#if defined(OS_LINUX)
    void SetIOThreadPriority(base::ThreadPriority io_thread_priority);
#endif

    // Getter for the one ChildProcess object for this process. Can only be called
    // on the main thread.
    static ChildProcess* current();

    static void WaitForDebugger(const std::string& label);

private:
    // Initializes TaskScheduler. May be overridden to initialize TaskScheduler
    // with custom arguments.
    virtual void InitializeTaskScheduler();

    int ref_count_;

    // An event that will be signalled when we shutdown.
    base::WaitableEvent shutdown_event_;

    // The thread that handles IO events.
    base::Thread io_thread_;

    // NOTE: make sure that main_thread_ is listed after shutdown_event_, since
    // it depends on it (indirectly through IPC::SyncChannel).  Same for
    // io_thread_.
    std::unique_ptr<ChildThreadImpl> main_thread_;

    // Whether this ChildProcess initialized TaskScheduler.
    bool initialized_task_scheduler_ = false;

    DISALLOW_COPY_AND_ASSIGN(ChildProcess);
};

} // namespace content

#endif // CONTENT_CHILD_CHILD_PROCESS_H_
